What does this research mean for the field?

The enteric virus associated with baby chick nephropathy in Japan is genetically identified as chicken astrovirus, not avian nephritis virus. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.CHALLENGES_CONSENSUS.

What question did this study set out to answer?

To clarify the viral cause of baby chick nephropathy in Japan, previously attributed to avian nephritis virus.

February 25, 2026Journal of Veterinary Medical Science0 citationsOpen Access

The enteric virus associated with baby chick nephropathy in Japan was genetically identified as chicken astrovirus, not avian nephritis virus

MMMasaji MaseNational Agriculture and Food Research Organization KHKanae HiramatsuNational Agriculture and Food Research Organization SWSatoko WatanabeNational Agriculture and Food Research Organization

Key Points

To clarify the viral cause of baby chick nephropathy in Japan, previously attributed to avian nephritis virus.
Conducted genetic analysis of virus samples from 1989 outbreak and 2020 isolates.
Performed phylogenetic analysis based on the open reading frame 2 gene.
Classified the identified virus within the subgroup Bi.
Identified virus as chicken astrovirus, distinct from avian nephritis virus.
Confirmed presence of CAstV in Japan since the 1980s.
Classified 2020 isolates as the only CAstV reported in Japan to date.

Abstract

In Japan, avian nephritis virus (ANV) isolates associated with the 1989 outbreak of baby chick nephropathy (BCN) were previously reported as pathologically and serologically distinct from known ANV strains. However, genetic analysis conducted in this study revealed that these viruses were actually chicken astrovirus (CAstV), first described in 2004, and genetically distinct from ANV. Phylogenetic analysis based on the open reading frame 2 (ORF2) gene, which encodes the viral capsid protein, classified this virus within the subgroup Bi, along with isolates from Saga Prefecture in 2020 which were the only CAstV reported in Japan to date. These findings suggest that CAstV was already present in Japan in the 1980s, predating its first global report in 2004 and its first domestic report.

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